1. Field of the Invention
The present invention relates to power source noise control of a semiconductor device, and more specifically, noise control using an open stub.
2. Description of Related Art
In recent semiconductor integrated circuits, higher integration and higher synchronization speeds are realized, and clock skew is reduced for realizing high-speed stable operations. Therefore, timings of through currents are synchronized, and power source noise tends to increase. Furthermore, according to the increase in speed of a multi-pin integrated circuit, switching of an output buffer or the like causes synchronous switching noise which fluctuates the power source.
A circuit disclosed in Japanese Unexamined Patent Publication No. H09(1997)-260522 is shown in FIG. 9. FIG. 9 is an example of an equivalent circuit when it is fixed to a package consisting of an insulator with a semiconductor element mounted and a board. In this figure, an integrated circuit is indicated by a, a PGA package is indicated by b, and a board is indicated by c. For example, in the PGA package b and the board c, inductances L101 and L102 and resistances are parasitically generated, and within the integrated circuit a, an input buffer 102 and an output buffer 103 are formed, and the former buffer is electrically connected to a pad 104 formed within the integrated circuit a. Furthermore, on the board c, a VDD terminal 105, a VSS terminal 106, and a 5V power source 107 are provided, and a band filter 108 provided in the PGA package is electrically connected to the VDD terminal 105. Therefore, in the conventional invention, a frequency as a main component of noise is cut by the band filter 108 to reduce noise at the D point. As described above, by providing a 40 mm band filter 108 between the input and output power sources, only the frequency of the main component of noise is cut off and noise propagation is prevented.
As techniques relating to the description given above, Japanese Unexamined Patent Publications No. 2002-76967 and No. H08(1996)-162803 are disclosed.